Insects such as beetles, butterflies, flies
and ants have larvae that are simply eating machines. They
have a soft flexible body which contains their digestive
system. Although their mouthparts may be well developed, their
senses are poorly developed. In most cases this type of larva
is surrounded by its food or it has food brought to it by
adult insects. The larval stage of insects can last from a few
weeks to over a year depending upon the species.

This simple larva changes dramatically to
become an adult which has wings, reproductive organs and
sophisticated sense organs. A resting stage is needed between
the larva and the adult; it is called a pupa (pl. pupae).

Inside the pupa all the body tissues of the
larva are rearranged. This can take from a few days to two or
three weeks depending upon the species of insect. Some
insects, however, pass through winter as pupae, so this stage
in their life cycle can last for several months.

When metamorphosis is complete and all the
tissues have been rearranged the adult will emerge from the
pupa. The skin of the pupa splits and the adult pulls itself
free. At first the exoskeleton is soft. The wings are inflated
with blood to make them expand. The adult insect must rest
while its wings dry and the exoskeleton hardens.

This dramatic transformation from larva to pupa and finally
to an adult insect is called complete metamorphosis.